What is the process by which molecules pass through a membrane to equalize concentration?

Diffusion is the process by which molecules move from an area of higher concentration to an area of lower concentration until equilibrium is reached. This movement occurs due to the natural kinetic energy of the molecules, allowing them to spread out evenly in the available space.

In biological systems, diffusion is essential for many physiological processes, such as the exchange of gases in the lungs, the distribution of nutrients and ions across cell membranes, and the movement of signaling molecules. It is a passive transport mechanism, meaning it does not require input of energy to occur, distinguishing it from processes like active transport, which involves energy to move substances against their concentration gradient.

In the context of the question, diffusion specifically pertains to the equalization of concentration gradients across a membrane, which is a fundamental concept in understanding cellular function and homeostasis in the human body.